Klaus Von Hertzon
クラウス・フォン・ヘルゼン
He collects Bakugan and has their open forms on a wall in his house in Germany, but he also collects other things such as suits of armor.
His attribute is Aquos and his Guardian Bakugan is Aquos Sirenoid, who he shares a bond with. He was Marucho’s rival because he sent Preyas to the Doom Dimension in their first battle.